Draft control for furnaces



p l 2, 1929- H. J. SAUVAGE 1,707,281

DRnt'T CONTROL FURNACES Filed 0 1 30, 1925 '2 Sheets-Sheet 1 Hekbf/Z ffiaz/zq'ge 1 Q; g, K WW6 5 W.

April 2, 1929- H. J. SAUVAGE 1,707,281

DRAFT CONTROL FOR FURNACES Filed O t. 30, 1925 2 Sheets-Sheet 2 Patented Apr. 2, 1929.

UNITED STATES 1,707,281 PATENT OFFICE.

HERBERT J. SAUVAGE, or CHICAGO, ILLInoIs, 'AssIeNoa r nnrmeflsi'sraus, me,

or CHICAGO, ILLINOIS, A CORPORATION or ILLINOIS.

DRAFT CONTROL FOR FURNACES I I Application filed October 30, 1925. Serial No. 65, 790.

This invention relates to improvements in oil burning furnaces and the like, and more particularly -to furnaces having automatically started and operated burners.

It is found that a large amount of the carbon or soot accumulated in the furnaces zo' feelumn in the exhaust flues and the stack inmotion while the flame is being lighted; to provide suitable auxiliary mechanism for starting the draft; and to provide automatic controls for the same.

The objects of the invention are accomplished by the mechanism illustrated in the accompanying drawings, in which:

Fig. 1 is a diagrammatic view showing a furnace including the auxiliary draft means, control instruments and circuits relating to the same.

Fig. 2 is a plan view, on a larger scale, g f the parts located by the line 2-2 of Fig. 3 is a section on line 3-3 of Fig. 2.

The invention as illustrated in the drawings includes an auxiliary motor driven air impeller placed in the stack or exhaust flue, for drawing air and gas from the fire-box and reducing the static pressure therein. Suitable electrical controls are provided so that when the room thermostat operates to start up the furnace the impeller is put into action and starts the column of air moving upthe chimney. This causes a draft while the combustion is being initiated. As soon as the gas column in the chimney is heated sufficiently to maintain the draft by its natural tendency to rise, the impeller motor is automatically disconnected from theroom thermostat circuit. The means for controlling the relation between the impeller motor and the room thermostat comprises a switch operated by a pneumatic thermostat mounto the furnace. I

ed in the stack. This stack. thermostat a thermal element, or closed coil of tubing, mounted in the stack and connected to a motor element, or bellows,'which is in actuating relation with the impeller switch.

In the drawings the furnace 1 is provided with an electrically driven oil burner 2, and 3 represents the exhaust flue leading to the stack. Usually the exhaust flue or pipe 3 rises vertically and then bends to a horizontal lead which is ihserted in the stack opening. A fan or impeller 4 is inserted in the horizontal portion of the pipe 3 and for convenience in the average installation,

at an angle of approximately 45 through an' opening 5 in the side thereof. The fan 4 is mounted on the extended shaft 6 of the small motor 7 'which is mounted at the side of the pipe 3. The motor 7 is carried by a plate 8 projecting from the flange plate 9, which is secured .over the opening 5 by means of the screws 10 which thread into the inner reinforcing ring 11.

For controlling the furnace to maintain a .desired temperature in a room or place Where theheat of the furnace is utilized, a so wall thermostat 12 is provided. The thermostat operates to close its switch 13 at low temperature to start the furnace and o ens the switch at high temperature to shut In the exhaust flue 3 is mounted a pneumatic thermostat coil 14: which is connected by a small tube 15 to the bellows 16. When the bellows 16 is ex anded by increased 'temperature in the exhaust flue 3 heating the coil 14:, the contact member 17, on the free end of the bellows, raises the outer end of the fan motor control switch 18 and rotates the element 18 clockwise, as viewed in Fig.

1, about the fixed pivot 19 and opens the switch.

The auxiliary fan circuit 20 and the burner circuit 21 are both connected through the room thermostat 12. 'The fan circuit 20 includes the line 23, the wall thermostat 12, the stack temperature operated switch 18 and the fan motor 7; and the burner 'cir-. cuit 21 includes the line 23, the burner motor 2, and also the wall thermostat 12.

In starting, a lowv room temperature causes the wall thermostat switch 13 to close. This closes the burner circuit 21 and also the fan circuit 20 which is closed when combustion is not taking place and hot gases are not passing through the exhaust pipe 3. The burner starts to operate and the oil is ignited in any well-known manner which need not be shown herein, the auxiliary stack fan 4 is in operation and starts the column of air in the stack in motion. In this mannersuflicient draft is supplied to the cold burner to complete the combustion and prevent carbon being deposited.

As soon as the furnace temperature rises, the hot gases will maintain the draft without the auxiliary fan land the fan is shut off. The hot gases cause the fluid in the coil 14 to expand and set up a pressure which is communicated through the pipe 15 to expand the bellows 16, the switch 18 is opened and the fan motor circuit 20 is broken.

The burner 2 remains in circuit wlth the room thermostat 12 and the furnace continues to operateuntil a high room tempera ture opens the thermostat switch 13. As soon as the exhaust flue 3 cools the fan motor switch 18 closes and the fan motor 7 again in circuit with the room thermostat As above stated, it has been found that, when no auxiliary meansare provided for an initial draft, large amounts of carbon are deposited when the combustion is being started. But with this invention in use the gases are immediately started in motion in the right direction and no carbon is deposited, the static pressure within the furnace is reduced, and the danger of a puff or back pressure blowing out the pilot light or sendlng fumes through the furnace doors is avoided. I

One embodiment has been shown and described for illustrative purposes only and many omissions and alterations may be made without departing from the spirit of the invention.

. jcct to heat of combustion for discontinuing the operation of the second mentioned means at a predetermined temperature.

2. In combination, in an automatically fired furnace having an automatically operatcd burner and an exhaust gas flue, auxiliary means for supplying an initial draft, and means operable by the ten'lperature in said flue for rendering said means operative and inoperative when the furnace is inoperative or in operation respectively.

3. In an automatically fired furnace having an electrically operated burner and an exhaust flue, an electrically o )erated fan in said flue, a room thermostat for controlling the burner and the fan, and a thermostat operated by the temperature in said flue and adapted to render said fan inoperative when the flue temperature rises.

4. In an automatically fired furnace, a fan mounted in an exhaust gas flue, a motor for driving said fan, a thermostat element in the exhaust flue, a room thermostat including a switch, a switch for said motor, and an electrically operated burner for the furnace,

a fan motor circuit passing through said thermostat switch, the motor switch and the motor, a burner circuit passing through the thermostat switch, and through the burner, both of said circuits including a source of current, and a bellows actuated by said thermostat element and adapted to open said motor switch when the temperature in the exhaust flue rises to a predetermined degree.

Signed at Chicago this 27th day of October, 1925.

HERBERT J. SAUVAGE. 

